Oxy-fuel burners for burning pulverized fuel generally comprise a central tube through which pulverized fuel, for example pulverized coal is blown by a stream of air. Oxygen is introduced in a passageway around (concentric to) the central tube and mixes with the pulverized fuel at the tip of the oxy-fuel burner
One of the problems with this arrangement is that the pulverised fuel can be very abrasive. As a result the wall of the central tube, which is usually made from stainless steel, has to be checked frequently. If the wall of the central tube fails in an oxy-fuel burner then the pulverised fuel may mix with the oxygen inside the burner and explode with very serious consequences.
This problem can be mitigated to some extent in an oxygen/natural gas/pulverised fuel burner by surrounding the central tube with the natural gas supply passageway However, both the wall of the central tube and the natural gas supply passageway can erode to bring both the natural gas and pulverized fuel into direct contact with the oxygen.